Modern aircraft have increasingly sophisticated control and communication systems. Included in many modern aircraft is an power supply bus that provides power and communication links between a variety of navigation, control and communication equipment. As the complexity of the aircraft has increased, the avionics system requirements have likewise increased. Furthermore, because of the numerous critical operations supported by the power supply bus, the reliability and performance of the power supply bus is of utmost importance.
One function provided by the power supply bus is to distribute power to various avionics components connected to the bus. For example, the power supply bus can provide operational power for navigation and communication radios, gauges, sensors and display units. The ability of the power supply bus to reliably power these avionics components is one key in the overall reliability of the aircraft.
One significant issue in power supply bus reliability is the large currents that can occur on system startup. In a typical system, the power supply bus is heavily loaded. On system startup, a large in rush of current is associated with turning on the power supply bus and its associated avionic components. This in-rush current can be 100 times the normal operating current of the power supply bus. Such an in-rush current can prematurely wear switches and other devices that make up the bus, and thus can reduce the reliability of the bus. For example, large in-rush currents associated with turning on an avionics master switch can actually damage the master switch itself.
Unfortunately, current avionic power supply bus systems have no reliable method for reducing the effects of large in-rush currents associated with system startup. Thus, what is needed is a system and method for limiting in-rush current on system startup of an avionics bus system.